EP2626051A1

EP2626051A1 - Apparatus for unloading a user's body weight during a physical activity of said user, particularly for gait training of said user

Info

Publication number: EP2626051A1
Application number: EP12154778.0A
Authority: EP
Inventors: Heike Vallery
Original assignee: Lutz Medical Engineering; Eidgenoessische Technische Hochschule Zurich ETHZ; Universitaet Zuerich
Current assignee: Lutz Medical Engineering; Eidgenoessische Technische Hochschule Zurich ETHZ; Universitaet Zuerich
Priority date: 2012-02-09
Filing date: 2012-02-09
Publication date: 2013-08-14
Also published as: US20150320632A1; EP2811962B1; JP5922800B2; WO2013117750A1; AU2013217939B2; US20180055715A1; US10470965B2; US9801775B2; CA2861575A1; DE202013012800U1; JP2015511151A; EP2811962A1; DE202013012799U1; AU2013217939A1; CA2861575C

Abstract

The invention relates to an apparatus (1) for unloading a user's body weight during a physical activity of said user (4), particularly for gait training of said user (4), comprising: a plurality of ropes (41, 42, 43, 44), wherein each rope (41, 42, 43, 44) extends from an associated drive unit (510, 520, 530, 540), is deflected by a passively displaceable deflection device, and then runs to a first free end (41a, 42a, 43a, 44a) of the respective rope (41, 42, 43, 44), and a node (60) being coupled to said first free ends (41a, 42a, 43a, 44a) and being designed to be coupled to said user (4), wherein the drive units (510, 520, 530, 540) are designed to retract and release the respective rope (41, 42, 43, 44) so as to adjust a current rope force ( F _R) along the respective rope (41, 42, 43, 44), which current rope forces add to a current resulting force (F) exerted on said user (4) via said node (60) in order to unload the user (4) upon said physical activity. Further, the invention relates to a method for controlling such a system.

Description

The invention relates to an apparatus, particularly for (guidedly) unloading a user's body weight during a physical activity of said user, particularly for gait training of said user (e.g. patient). Of course, also animals, robots or any other object may be unloaded by the apparatus according to the invention. Thus, the term "user" may specifically refer to a human person, but may also mean any other object that is to unload.
Typically, in known devices of this kind, a user is statically suspended from a lift line while walking on a treadmill. Thus, the sort of physical activities (trainings) that can be performed by the user are rather limited.
Based on the above, the problem underlying the present invention therefore is to provide for an apparatus that allows for a variety of different physical activities or movements while safely supporting the user (object) at the same time in a defined manner.
This problem is solved by a device having the features of claim 1 as well as by a method having the features of claim 13.
According thereto, the apparatus according to the invention comprises a plurality of ropes, wherein each rope is coupled to an associated drive unit being particularly connected to a suitable rigid support structure (for example a support frame or a ceiling) and extends from the respective drive unit to a (uniquely associated) deflection device for deflecting the respective rope and then to a first free end of the respective rope, and a node being coupled to said first free ends and being designed to be coupled to said user, wherein the drive units are designed to retract and release (e.g. wind and unwind) the respective rope so as to generate a current rope force along the respective rope, which current rope forces add to a current resulting force exerted on said user via said node in order to continuously unload the user upon said physical activity. Preferably, the deflection devices are passively displaceable (i.e. can change their position in space, particularly in a guided manner), which particularly means that they do not themselves comprise a movement generating means for moving the respective deflection device actively, but can be displaced by forces induced into the deflection devices via the ropes (in a passive manner). Particularly, the deflection devices may be connected to each other (for instance pairwise such that the respective two deflection devices can be displaced together while maintaining a constant distance between the deflections devices along the direction of displacement), and they may be guided by a guide rail or a plurality of guide rails or may be suspended from a support structure (e.g. support frame or ceiling of a room), particularly by means of a wire or another (elongated) supporting element such that their centers of mass can (passively) change position in space. Likewise, said guide rail(s) may be connected to a support structure (e.g. support frame or ceiling). A connection between two (or even more) deflection elements can be provided by means of a (separate) connecting means (element), which may be interchangeable. However, deflection devices may also be integrally connected to each other (i.e. form a single piece).
The rope forces may be controlled such that the resulting rope force is a purely vertically acting force, but may also have components in the horizontal plane so as to direct the user in a certain direction upon said physical activity (e.g. gait training).
Preferably, the apparatus according to the invention is configured such that a user (or object) coupled to the node as intended can in principle perform a movement in a three dimensional space, i.e., is able to move horizontally, namely forwards backwards and also sideways, as well as vertically (e.g. climbing a staircase or some other object such as an inclined surface provided in the horizontally extending space accessible to the user being coupled to the node), and can rotate about the vertical axis, allowing walking curves or turning. Of course, the apparatus according to the invention can also be combined with known devices such as a treadmill etc.
According to an aspect of the invention, the support frame comprises an upper frame part extending along a horizontal extension plane, wherein the support frame may comprise a plurality of vertically extending leg members via which the upper frame part can be supported on a floor.
According to a further aspect of the invention, each of the ropes interacts with an associated rope force sensor for determining the currently acting rope forces and thereby the current resulting force on the user. Alternatively, the current rope forces may be detected by means of electrical current sensors interacting with the drive units (for instance such sensors may be integrated into the actuators of the winches). Preferably, these rope force sensors provide (analog) output signals corresponding to the currently acting rope forces (current rope forces).
In an embodiment of the invention, said output signals are transmitted via a processing means which digitizes said output signals to a controlling unit that is able to determine the currently acting rope forces by means of said output signals provided by the rope force sensors.
According to an aspect of the invention, the controlling unit is designed to control said current resulting force (on the node/user) either directly via said drive units or indirectly by controlling said rope forces (i.e., the individual rope forces acting on the node) in an (inner) control loop in order to adjust said current resulting force for unloading (and eventually also pulling) the user in a pre-defined manner, wherein the controlling unit is preferably designed to calculate a currently desired (reference) rope force for each of the ropes and to control the drive units accordingly such that the current rope forces as determined with help of the respective rope force sensor (or another sensor) match (approach) the respectively desired rope force at least asymptotically after a certain period of time. Of course controlling is preferably conducted continuously, wherein particularly the desired rope forces (desired resulting force) and current rope forces (current resulting force) may be repeatedly calculated/sensed (at a constant rate). Alternatively (or in addition), the controlling unit may be designed to control the drive units such that the current (spatial) position of the node (e.g. with respect to a space-fixed coordinate system or with respect to said apparatus) approaches a (currently) desired position of the node.
In an embodiment of the invention, the apparatus comprises at least two ropes, preferably four ropes, namely a first, a second, a third and a fourth rope (preferably, but not necessarily, there is an even number of ropes). Preferably, the first rope extends from its associated drive unit towards a first deflection device, is deflected by the first deflection device and then connects to the node. Likewise, the second rope preferably extends from its associated drive unit towards a second deflection device, is deflected by the second deflection device and then connects to the node. Further, also the third rope (if present) preferably extends from its associated drive unit towards a third deflection device, is deflected by the third deflection device and then connects to the node. Finally, also the fourth rope (if present) extends from its associated drive unit towards a fourth deflection device, is deflected by the fourth deflection device and then connects to the node. Preferably, two or more deflection devices are connected to each other to form a deflection unit, so that their combined movement is governed by (multiple) rope forces acting on them.
In an aspect of the invention, each rope may be connected to the node via a spring element.
Particularly, the rope force sensors may be formed with help of such spring elements (being inserted into the respective rope) in combination with a means to measure the length of the respective spring element, e.g. a linear encoder or a wire sensor, which may be a cable-extension transducer comprising a measuring cable wound on a cylinder (spool) coupled to a shaft of a rotational sensor (e.g. a potentiometer), wherein the respective rotational sensor is connected to an end of the respective spring element and wherein the respective measuring cable is connected to another end of the respective spring element. In case the transducer's measuring cable is now unreeled or reeled from the cylinder when the respective spring element is elongated or contracted, the cylinder and shaft rotate accordingly, thus creating an (electrical) output signal of the rotational sensor proportional to the measuring cable's linear extension. Knowing the spring constant of the respective spring element, the rope force can thus be determined via the spring force of the respective spring element. In this regard, it is to be noted that any other force sensor may also be employed in order to measure the individual rope forces acting on the ropes. Preferably, the force sensor is located close to the node, but it can also be located closer to the respective drive unit or winch, or even be based on measurement of the electrical current of the respective drive unit (e.g. actuator driving the respective winch).
According to an aspect of the invention, the apparatus comprises at least a first guide rail (for instance in case of two ropes and two deflection devices), preferably also a second guide rail, each running along a longitudinal axis. These longitudinal axes preferably extend horizontally with respect to an operating position of the apparatus, in which the apparatus can be operated (e.g. by the user) as intended. Preferably, the guide rail(s) can be connected to said support structure (e.g. support frame or ceiling of a room, in which the apparatus is arranged). In case of a support frame, the guide rail(s) may be connected to said upper frame part. Preferably, the guide rails are arranged such that they run parallel with respect to each other. Particularly, in case of two guide rails, each guide rail may be tilted about its longitudinal axis, particularly by an angle of 45°.
Preferably, the first and the second deflection device are slidably connected to the first guide rail, so that they can slide along the first guide rail along the longitudinal axis of the first guide rail. In case of four ropes, the third and the fourth deflection device are preferably slidably connected to the second guide rail, so that they can slide along the second guide rail along the longitudinal axis of the second guide rail.
In detail, the individual deflection devices may comprise a base (e.g. in the form of a cart) via which the respective deflection device can be slidably connected to the associated guide rail, and wherein each deflection device particularly comprises an arm hinged to the base of the respective deflection device so that the respective arm can be pivoted with respect to the respective base about a pivoting axis running parallel to the longitudinal axis of the respective guide rail. Further, the deflection devices may each comprise a deflection element connected to the respective arm, around which deflection element the respective rope is laid for deflecting said rope, and wherein the respective deflection element may be formed by roller that is rotatably supported on the respective arm, so that particularly the respective roller can be rotated about a rotation axis that runs across the longitudinal axis of the respective guide rail. Further, an arresting means may be provided for each deflection device for arresting the respective deflection device with respect to the associated guide rail, for instance when using the apparatus with a treadmill.
According to a further aspect of the invention, the first and second deflection device are connected by a connecting element (or by an integral connection), so as to form a first deflection unit (also denoted as first trolley), likewise, in case of four ropes, the third and the fourth deflection device are preferably connected by a further connecting element (or by an integral connection), so as to form a second deflection unit (also denoted as second trolley), wherein particularly said connecting elements comprise the same length along the longitudinal axis of the respective guide rail. Further, the connecting elements may be designed to releasably connect the associated deflection devices, in order to be able to substitute a connecting element with a connecting element having a different length along the respective longitudinal axis. Further, the respective connecting element may be a flexible rope member or a rigid rod (particularly produced out of a carbon fibre composite).
Preferably, the drive unit of the first rope and the drive unit of the second rope face each other along the longitudinal axis of the first guide rail, wherein the first deflection unit is arranged between said drive units along the longitudinal axis of the first guide rail. In a similar manner, in case of four ropes, additionally also the drive unit of the third rope and the drive unit of the fourth rope face each other along the longitudinal axis of the second guide rail, wherein the second deflection unit is arranged between said drive units along the longitudinal axis of the second guide rail. Preferably, the drive units are arranged on the corners of a rectangle.
According to a further aspect of the invention, the drive units each comprise an actuator (particularly a servo motor) being connected to a winch, around which the respective rope is wound, particularly via a flexible coupling, wherein the respective actuator is designed to exert a torque on the respective winch via a drive axis of the respective winch so as to retract or release the respective rope, i.e. to adjust the length of the respective rope that is unwound from the winch. Optionally, the respective drive unit may comprise a brake for arresting the respective winch. Further, in order to prevent the respective rope from jumping off the associated winch or over a thread, the respective drive unit preferably comprises at least one pressing member, particularly in the form of a pressure roller, that presses the respective rope being wound around the associated winch with a pre-definable pressure against the winch.
According to a further aspect of the invention, the drive units may be coupled to an actuator unloading system that is designed to compensate for the weight that is to be unloaded so that the actuators do not have to permanently exert a torque on the winches, but are merely needed to support changes in movement.
According to yet another aspect of the invention, the apparatus comprises a sensor means for determining a current state of the apparatus as well as the position of the user (node) with respect to the apparatus or a space-fixed coordinate system. Particularly, said current state is given by the lengths of the ropes being unwound from the respective winch and the positions of the deflection units along the respective guide rail.
In detail, the lengths unwound from the winches (i.e. the length of the portion of the respective rope that is unwound from the respective winch) is preferably detected by multi turn encoders being coupled to the drive axes of the winches, respectively. Other sensors (e.g. cable-extension transducers may also be employed for determining said lengths).
Further, from output signals provided by said multi turn encoders, the position of the node can also be determined by means of the controlling unit. Furthermore, the positions of the deflection units along the respective guide rails may be each captured by means of an associated optical laser distance sensor, which distance sensors may be arranged at a free end of each guide rail, and whose output signals may also be digitized by a signal processing unit and further transmitted to the controlling unit.
Further, for determining the acceleration of the node, an acceleration sensor may be provided on the node, being capable of sensing the acceleration of the node along three orthogonal axes. The node may comprise an upper and a lower node member being rotatably connected to each other, wherein the ropes are connected to the upper node member and wherein a bail (see below) may be connected to the lower node member, such that the bail can be rotated about the vertical axis. For determining an angular velocity of the node (i.e. of the upper node member), a gyroscope may be provided on the node. Furthermore, for sensing a rotation angle of said bail about the vertical axis a potentiometer may be provided on the node that measures the angle between the upper and the lower member (part) of the node. Also the acceleration sensor, the gyroscope and the potentiometer may provide analog output signals representing the respective quantity to be sensed, wherein particularly the latter three sensors are preferably connected to a signal processing unit that is configured to digitize the respective output signals and to transmit them to the controlling unit, wherein said signal processing unit is preferably connected to the node by means of a flexible data line.
In the examples above the controlling unit may be designed to further process and/or analyze said (digitized) output signals provided by the individual sensors so as to determine the respective quantity, like the lengths of the ropes being unwound from the winches, the positions of the deflection units, or the position of the node (user).
Especially, the acceleration sensor, the gyroscope and the potentiometer may be used to enhance position detection of the user and the node.
According to a further preferred aspect of the invention, the controlling unit is designed to control the drive units, particularly the torque exerted by the respective actuator onto the respective winch, particularly depending on a current state of the apparatus and/or the spatial position of the user determined with help of the aforedescribed sensor means, such that the current resulting force on the user approaches (matches) the desired resulting force on the user or that the current position of the user (node) approaches (matches) a currently desired position (reference) of the user (node). In particular, the controlling unit can control this current resulting force either directly, i.e. by sending control signals to the drive units as a function of the error (e.g. difference) between a (currently) desired resulting force and the current resulting force, or indirectly, by controlling the current rope forces by means of a control loop denoted as inner control loop or inner loop.
To control the current resulting force directly, without such an inner loop, the controlling unit may be configured to apply a pre-defined torque to a plurality of the drive units at the same time as a function of said error in the current resulting force, in order to provide for a fast reaction in highly dynamical situations, for instance. Thus, in case the walking direction of the user is pointing along the longitudinal axes of the guide rails for example, the controlling unit may be designed to perform a lateral correction on the user by commanding the respective drive units to pull the ropes of the first or the second deflection unit at the same time by the same amount. Likewise, the controlling unit may be designed to perform a forward or backward correction on the user by commanding the respective drive units to pull those two corresponding ropes at the same time by the same amount that oppose each other across the longitudinal axes of the guide rails.
In case of said indirect controlling said inner loop (provided by the controlling unit) is used to calculate the desired rope forces being a reference for said inner loop by requiring a desired static equilibrium, where

there is force equilibrium on the node,
there is force equilibrium on the deflection units, and
the deflection units both reside in the same position along the respective guide rail.

Preferably, the controlling unit is configured to control the torques applied to the individual winches according to the following control law used by the controlling unit $u = i F_{R, des} + K_{r} (F_{R, des} - F_{R}) + u_{ff},$
with $F_{R, des} \in R^{nx 1}$
being the calculated reference rope forces (for example calculated according to said indirect control), $i \in R$
being the transmission ratio of the respective winch, $K_{r} \in R^{nxn}$
being a positive definite rope force feedback matrix containing feedback gains, $n \in N$
being the number of ropes (e.g. four), and $u_{ff} \in R^{nx 1}$
being an optional additional term going to zero in static conditions of the apparatus by means of which a pre-defined torque can be applied to a plurality of the winches at the same time (for example calculated according to said direct control).
According to a further aspect of the invention, the controlling unit may also be configured to control said torques such that a current position of the node approaches a respective desired position of the node.
Further, the afore-mentioned bail particularly comprises two opposing free ends, wherein particularly each of the two free ends comprises a receptacle (for instance in the form of a hook formed by the bail) for receiving a connection element for connecting a harness to the bail, which harness is to be put on by the user for connecting the latter to the node (via the connection elements and the bail). In a variant of the invention the connection elements are designed to be length adjustable for adapting the apparatus to the height of a user, for instance.
The signal processing unit that may connect to the acceleration sensor, the gyroscope, and the potentiometer (see above) may also be connected to the rope force sensors provided on the node, preferably through a (flexible) data line (cable). The signal processing unit thereby transmits output signals provided from the rope force sensors to the controlling unit, where they can be further processed.
For enabling the signal processing unit to follow the node upon movement of the node, the signal processing unit is preferably slidably connected to one of the guide rails. The signal processing unit may be driven by a further drive unit, wherein particularly the controlling unit is designed to also control the position of the signal processing unit along the guide rail depending on the position of the node and the signal processing unit along the guide rail, so as to maintain a constant distance between the node and the moveable signal processing unit along the respective guide rail. The respective position of the movable signal processing unit may be sensed with a suitable sensor and compared to the current position of the node by the controlling unit.
The problem according to the invention is further solved by a method for controlling an apparatus for unloading, particularly the body weight of a user during a physical activity, as claimed in claim 13, wherein the method particularly uses an apparatus according to the invention.
According thereto, the method according to the invention comprises the steps of:

particularly determining a current state of a system of a plurality of ropes each being connected to a node via a first free end of the respective rope, to which node a user (being enabled to displace the node horizontally and also vertically upon walking) or an object is coupled, which ropes can each be wound onto and unwound from a respective winch in order to adjust the rope forces acting along the respective ropes on the node, wherein the ropes are each deflected by a (uniquely) associated deflection device, which deflection devices are each (passively) movable (e.g. along a first direction) and particularly connected to each other, particularly as described above,
particularly determining the position of the user (with respect to the apparatus or a space-fixed coordinate system),
calculating a torque for each of the winches depending on the current state of the apparatus and the position of the user, such that the force on the user approaches (matches) the respective desired force on the user or that the current position of the user (node) approaches a (currently) desired position of the user (node), and
exerting the respective torque onto the associated winches in order to let the current resulting force on the user (object) approach the (currently) desired resulting force.

Preferably, the deflection devices are grouped in pairs (or may comprise even more deflection devices), wherein the deflection devices of each pair are designed to be displaced together (i.e. maintaining a constant distance with respect to each other while being passively displaced), which pairs are denoted as deflection units. Particularly at least two ropes are provided that are deflected by a first deflection unit that may be passively displaceable along a first direction (x-direction). Preferably, four ropes are provided, wherein the first and the second rope are deflected by the first deflection unit and the third and fourth rope are deflected by a second deflection unit being passively displaceable along the first direction (parallel to the first deflection unit).
Particularly, said current state is defined by the lengths of the ropes being unwound from the respective winch and the position(s) of the deflection unit(s) along the first direction.
Furthermore, the current torques for the winches are preferably calculated either directly based on the current error (e.g. difference) between a desired resulting force on the user and the current resulting force on the user, or indirectly, by controlling the individual rope forces in a control loop denoted as inner control loop or inner loop (see also the corresponding description above). In the latter case, the desired rope force for each of the ropes is preferably determined from a desired static equilibrium, where

there is force equilibrium on the node,
there is force equilibrium on the deflection unit(s), and
the deflection units both reside in the same position along the first direction (in case there are a two or more deflection units).

Here, the controlling unit is preferably designed to control the drive units (command torques to the drive units) such that the current rope forces approach the calculated desired rope forces.
In case of direct control of the force on the user, the method according to the invention may provide for applying a pre-defined torque to a plurality of the winches at the same time, particularly in order to let the current resulting force F on the user approach the desired resulting force F _des on the user faster.
Particularly, the torques u (applied to the individual winches) may be determined according to $u = i F_{R, des} + K_{r} (F_{R, des} - F_{R}) + u_{ff}$
as already discussed above, where F _R,_des are the desired rope forces (references), F _R are the current rope forces, K _r is a matrix containing feedback gains and u _ff is an optional additional term (being zero in static conditions of the apparatus) by means of which a pre-defined torque can be applied to a plurality of the winches at the same time, so as to achieve the control goal as fast as possible in dynamic situations (e.g. fast movements of the node/user). Particularly, this allows for preventing the user from falling.
Regarding controlling it is also referred to the corresponding descriptions above.
It is to be noted that the use of the apparatus as described herein is not limited to medical uses, but may also be employed in any other field of transportation and unloading of objects, particularly in the field of construction.
Further features and advantages of the invention shall be described by means of a detailed description of embodiments with reference to the Figures, wherein

Fig. 1: shows an exemplary support frame of an apparatus according to the invention;
Fig. 2: shows a perspective view of the ropes, drive units, deflection units and the moveable signal processing unit;
Fig. 3: shows a perspective view of a drive unit according to Fig. 2;
Fig. 4: a perspective view of the spring elements, the rope force sensors, the node and the bail of the apparatus according to the invention;
Fig. 5: a perspective view of a deflection device (unit) of the apparatus according to the invention;
Fig. 6: a closer perspective view of the spring elements, the node, the rope force sensors and the bail of the apparatus according to the invention,
Fig. 7: a schematical, perspective view of the apparatus according to the invention when used by a user; and
Fig. 8: a schematical perspective view of an arresting means for arresting a deflection device of the apparatus according to the invention.

Figure 1 shows in conjunction with Figs. 2 to 8 an apparatus 1 according to the invention for guidedly unloading a user 2 upon a physical activity (e.g. gait training as shown in Fig. 7).
The apparatus 1 comprises a suitable support structure (e.g. support frame) 10 having an upper frame part 100 being supported by a plurality of vertically extending leg members 101, such that the leg members 101 confine (together with the upper frame part 100) a three-dimensional working space 3, in which the user 4 can move along the horizontal x-y-plane (as well as vertically in case corresponding objects, e.g. inclined surfaces, staircases etc., are provided in the working space 3). Alternatively, a ceiling of a room can be used as a support structure. Said working space 3 then extends below said ceiling.
The upper frame part 100 is formed by two parallel longitudinal members 102 extending along the x-direction and five parallel cross members 103 extending along the y-direction and connecting the two longitudinal members 102. The longitudinal and cross members 102, 103 span the horizontally extending upper frame part 100.
A first and a second guiding rail 21, 22 are attached to the support structure 10 (e.g. to the upper frame part 100), wherein the two guide rails 21, 22 each extend along a respective longitudinal axis L, L'. The first guide rail 21 is designed to slidably support a first and a second deflection device 31, 32 as shown in Fig. 2, whereas the second guide rail 22 is designed to slidably support a third and a fourth deflection device 33, 34. Here, the first and the second 31, 32 as well as the third and the fourth deflection device 33, 34 are connected by a rigid connecting means 350, 360 so that the two pairs of deflection devices 31, 32, 33, 34 each form a deflection unit (trolley) 35, 36, which can slide along the respective guide rail 21, 22. Preferably, the guide rails 21, 22 are pivoted by an angle W=45°C as shown in Fig. 5.
As indicated in Fig. 8, each deflection device 31, 32, 33, 34 may be arrested with respect to the associated guide rail 21, 22 by means of an arresting element C. Such an element C can be a separate element providing a stop for a deflection device 31, 32, 33, 34 but may also be integrated into a deflection device 31, 32, 33, 34 and may be designed to clamp the respective deflection device 31, 32, 33, 34 to the respective guide rail 21, 22. Particularly, arrested deflection devices 31, 32, 33, 34 may be used when the apparatus 1 is used with a treadmill.
Each deflection unit 35, 36 is configured to deflect two ropes 41, 42, 43, 44 as shown in Fig. 2, for instance. The individual ropes 41, 42, 43, 44 each extend from a drive unit 510, 520, 530, 540 comprising a winch 511, 521, 531, 541, respectively, on which the respective rope 41, 42, 43, 44 is wound, to an associated deflection device 31, 32, 33, 34 of the respective deflection unit 35, 36. From the deflection devices 31, 32, 33, 34 the ropes 41, 42, 43, 44 extend towards a node 60, to which a first free end of each rope 41, 42, 43, 44 is connected via a spring element 71, 72, 73, 74 as shown in Figs. 2, 4 and 6 for instance.
The mounting positions D of the individual drive units 510, 520, 530, 540 are indicated in Fig. 1. Each deflection unit 35, 36 is associated to two drive units 510, 520; 530, 540, which are positioned on either side of the respective guide rail 21, 22 along the respective longitudinal axis L, L'.
In Fig. 5 a single deflection device 34 is shown (the others are constructed analogously), wherein the connecting element 360 connecting said device 34 to its neighboring counterpart (not shown) is indicated by dashed lines. The deflection device 34 comprises a base 340 that slidably engages with the respective guide rail 22 so as to allow for sliding the base 340 along the guide rail 22. A u-shaped arm 341 is pivotably hinged to two protruding regions 342, 343 of the base 340 such that the arm 341 can be pivoted about a pivoting axis A running along the x-direction (longitudinal axis L'). The arm 341 serves for bearing a deflection element 344 in the form of a roller being rotatable about a rotation axis A', around which roller 344 the respective rope 44 is laid for deflecting the latter.
In detail, as shown in Fig. 3, each drive unit 510, 520, 530, 540 comprises an actuator (servo motor) 512, 522, 532, 542 being connected via a (flexible) coupling 53 to a drive axis 55 of a winch 511, 521, 531, 541, on which the respective rope 41, 42, 43, 44 is wound. The respective winch 511, 521, 531, 541 and the respective actuator 512, 522, 532, 542 are mounted on a common platform 50, wherein two retaining elements 51, 52 protrude from the platform 50, on which elements 51, 52 the respective winch 511, 521, 531, 541 is rotatably supported. Further, the respective drive unit 510, 520, 530, 540 comprises at least one pressure roller 54 for pressing the respective rope 41, 42, 43, 44 against the associated winch 511, 521, 531, 541 so that the respective rope 41, 42, 43, 44 can be reeled an unreeled in a defined manner.
The drive units 510, 520, 530, 540 interact with a sensor means (that may consist of several individual sensors, see above) that is adapted to provide output signals that represent (or can be transformed into) the length s _w of (a portion of) the respective rope 41, 42, 43, 44 that is currently unwound from the respective winch 511, 521, 531, 541, the position s _T of the deflection units 35, 36 along the x-direction (i.e. along the respective guide rail 21, 22), as well as the position w of the node 60 (user 4).
As shown in Fig. 6, the ropes 41, 42, 43, 44 meet at the node 60, to which they are coupled via a spring element 71, 72, 73, 74, respectively. In order to be able to detect the rope forces F _R (c.f. Fig. 7) currently acting along the ropes 41, 42, 43, 44 onto the node 60 and thus onto the user 4, four rope force sensors 710, 720, 730, 740 in the form of cable-extension transducers are provided on the node 60, wherein the respective measuring cable 711, 721, 731, 741 of the respective transducer 710, 720, 730, 740 is connected to the first free end 41 a, 42a, 43a, 44a of the respective rope 41, 42, 43, 44 (either directly or via connection element connecting the respective spring element 71, 72, 73, 74 to the first free end 41a, 42a, 43a, 44a of the respective rope 41, 42, 43, 44) while the corresponding potentiometer 712, 722, 732, 742 is coupled to (an upper member of) the node 60. In case a spring element 71, 72, 73, 74 is elongated, the corresponding measuring cable 711, 721, 731, 741 is drawn out and the transducer (potentiometer) 710, 720, 730, 740 generates an output signal corresponding to the drawn-out length of the measuring cable 711, 721, 731, 741 corresponding to the rope force F _R currently acting on the respective rope 41, 42, 43, 44 (and thereby elongating the respective spring element 71, 72, 73, 74). However, any other conceivable force sensor may be applied as well for determining the rope forces. Further, dedicated force sensors in/on the ropes 41, 42, 43, 44 can be omitted. Instead sensors for sensing the electrical current of the winch actuators 512, 522, 532, 542 can be used in order to estimate the respective winch torque. Such a sensor may be associated to each drive unit/ winch 510, 520, 530, 540.
Further, the node 60 comprises ― with respect to an operating state of the apparatus 1 - an upper node member 61, which is connected to the cable- extension transducers 710, 720, 730, 740, and a lower node member 62 being rotatably supported on the upper node member 61, so that a horizontally extending bail 80 being coupled to the lower node member 62 can be rotated about a vertical axis z.
The node 60 may comprise an acceleration sensor 90 as well as a gyroscope 91 and a potentiometer 92 for sensing the acceleration of the node 60 along three orthogonal axes (for instance x, y and z), for sensing the angular velocity of the node 60 and for sensing a rotation angle of the bail 80 about said vertical axis z with respect to the upper node member 61. Corresponding output signals representing these quantities (or quantities that can be used to determine the desired quantities) are transmitted ― together with the output signals from the rope force sensors 710, 720, 730, 740 - via a flexible data line (cable) 93 extending from the node 60 to a movable signal processing unit 94 as shown in Fig. 2. The signal processing unit 94 is slidably supported on one of the guide rails 21, 22.
The signal processing unit 94 can be driven by a further drive unit, wherein preferably the movement of the signal processing unit (also called signal box) 94 is controlled by a controlling unit (not shown), to which the signal processing unit 94 is connected so that the controlling unit is able to use the output signals transmitted by the signal processing unit 94 for controlling of the apparatus 1. Particularly, the controlling unit is configured to control the movement of the signal processing unit 94 such that the distance between the node 60 and the signal processing unit 94 along the x-direction is constant. Particularly, the movement of the signal processing unit 94 along the respective guide rail 21, 22 (x-direction) is controlled such by the controlling unit that the signal processing unit is always arranged behind the node 60 (user 4) with respect to the current walking direction of the user 4.
As shown in Figure 7, the bail 80 is used for holding a harness 95 which is to be put on by the user 4. The harness 95 then supports the user 4 via two connection elements 96, 97 that are engaged with corresponding receptacles 81, 82 formed on the free ends of the bail 80, and via the node 60 to which the bail 80 is coupled.
Concerning controlling of the current resulting force F that is exerted onto the node 60, there are many ways in classical control theory how to approach tracking problems for nonlinear systems as the present one. For example, the system could be linearized and an optimal controller could be derived. In the following, controlling is described without loss of generality for four ropes, but may also be conducted analogously for two ropes or any larger number of ropes.
A simple but effective idea is to control said output force vector F indirectly, by controlling individual rope forces subsumed in the vector $F_{R} \in R^{4}$
in an inner loop. These rope forces F _R are functions of both the device states s, i.e., the lengths s_w of the unwound (portions of the) ropes 41, 42, 43, 44 and the deflection unit's 35, 36 positions s _T, and the user position w $F_{R} = h (s w)$
The three-dimensional force vector F acting on the subject 4 is given by the sum of the four individual rope force vectors F _R. Therefore, there would potentially be an infinite number of solutions for rope force vectors that give the same resulting force.
However, as stated above, the winch forces (torques) do not only affect rope forces, they also affect trolley (deflection unit) movement.
This can be used to formulate two additional control goals, which are a) to find a solution that is also valid in static conditions (Then, the sum of forces acting on the trolleys 35, 36 will be in equilibrium, and the position can be held), and b) to have the trolleys 35, 36 move in a similar way, so that they are always at the same position x (c.f. Fig. 7). For example, if a purely vertical force is desired and the person 4 is standing in the middle between the two linear guide rails 21, 22, the trolleys 35, 36 should be positioned such that the person 4 stands below the center of a square spanned by the pulleys (deflection devices) 31, 32, 33, 34.
The first goal can be formulated mathematically by requiring that in static conditions, where all speeds and accelerations are zero, $d s_{W} / d t = 0, d^{2} s_{W} / d t^{2} = 0, d s_{T} / d t = 0, d^{2} s_{T} / d t^{2} = 0, d w / d t = 0, d^{2} w / d t^{2} = 0,$
the correct force is applied on the user (object) 4, i.e. the current resulting force (output force) F of the controlling unit (controller) matches the desired resulting force F _des meaning equation F = F _des is fulfilled. The requirement is found by force equilibrium on the two trolleys 35, 36.
In summary, this yields 3 equations from force equilibrium on the node 60, further 2 equations from force equilibrium on the two trolleys 35, 36 in x-direction, and one equation commanding the two trolleys 35, 36 to be at the same position s _T in x-direction. These 6 equations can be used to find the four desired rope forces F _R,des and the two trolley positions.
Appropriate measures (for example saturations) can be taken to make sure the ropes 41, 42, 43, 44 always remain in tension.
The desired rope forces F _R can then be used as a reference for the individual feedback loops for each winch 511, 521, 531, 541.
For example, the control law could be $u = i F_{R, des} + K_{r} (F_{R, des} - F_{R}) + u_{ff}$
with F _R,des being the calculated desired (reference) rope forces, i the transmission ratio of the actuator-winch unit (drive unit) 510, 520, 530, 540, $K_{r} \in R^{4 \times 4}$
being a positive definite rope force feedback matrix containing feedback gains, and u _ff denoting potential additional terms that go to zero in static conditions. The first two terms will ensure that the system asymptotically approaches the desired forces on the person 4, at least when the person 4 stands still.
In order to make the system react fast in dynamic conditions, the terms u _ff can be used. One possibility is to use a type of "synergy control", where actuators 512, 522 532, 542 work in groups. For example, using a diagonal feedback matrix $K_{C} \in R^{3 \times 3},$
a virtual input vector u * in Cartesian space can be generated: $u^{*} = K_{c} (F_{des} - F) \in R^{3}$
This three-dimensional vector u * then needs to be mapped to the four winch torques u by a function ρ: $u = ρ u^{*} .$
Similar to human muscles, this function could encode synergies, which lump actuators 512, 522, 532, 542 into functional groups.
For example, if the force component acting on the user 4 in vertical direction z is too low compared to the reference, so u* _z > 0, all four winches 511, 521, 532, 541 could be pulling equally, which means that the vertical component u* _z would simply be commanded to all winches 511, 521, 532, 541 equally. The component in x-direction, which is parallel to the guide rails 21, 22, could be distributed such that the winches on one side (depending on the sign, these could be 511 and 531, cf. Fig. 2) act as a pair and both pull equally, whereas the opposite pair 521, 541 does not produce additional torques. Necessary corrections in the direction orthogonal to the guide rails 21, 22 could be distributed in an analog manner, with either the winch pair 511, 521 or 531, 541 pulling, depending on the sign. This type of control law leads to a fast correction of the forces acting on the user (object) 4, and it also accelerates the movement of the passive trolleys 35, 36 towards their "ideal" asymptotic positions. In static conditions, this part of the controller will not generate any torques u.

Claims

Apparatus, particularly for unloading a user's body weight during a physical activity of said user, particularly for gait training of said user, comprising:
- a plurality of ropes (41, 42, 43, 44), wherein each rope (41, 42, 43, 44) extends from an associated drive unit (510, 520, 530, 540) to an associated deflection device (31, 32, 33, 34), is deflected by the latter, and then extends to a first free end (41 a, 42a, 43a, 44a) of the respective rope (41, 42, 43, 44), wherein the deflection devices (31, 32, 33, 34) are designed to be passively displaceable, and

- a node (60) being coupled to said first free ends (41a, 42a, 43a, 44a) and being designed to be coupled to a user (4), wherein the drive units (510, 520, 530, 540) are designed to retract and release the respective rope (41, 42, 43, 44) so as to adjust a current rope force ( F _R) along the respective rope (41, 42, 43, 44), which current rope forces ( F _R) add to a current resulting force (F) exerted on said user (4) via said node (60) in order to unload the user (4), particularly upon said physical activity.
Apparatus according to claim 1, characterized in that each of the ropes (41, 42, 43, 44) interacts with an associated rope force sensor (710, 720, 730, 740) for determining the current rope forces ( F _R), wherein particularly the rope force sensors (710, 720, 730, 740) are arranged at the node (60), wherein particularly each rope (41, 42, 43, 44) is connected to the node (60) via an associated spring element (71, 72, 73, 74), wherein particularly the respective rope force sensor (710, 720, 730, 740) measures the length of the spring element (71, 72, 73, 74) corresponding to the respective current rope force ( F _R), wherein particularly the respective rope force sensor (710, 720, 730, 740) is formed by a cable-extension transducer comprising a measuring cable (711, 721, 731, 741) wound on a cylinder coupled to a shaft of a rotational sensor (712, 722, 732, 742), wherein particularly the rotational sensor (712, 722, 732, 742) is connected to the node (60) and wherein particularly the measuring cable (711, 721, 731, 741) is connected to the first free end (41 a, 42a, 43a, 44a) of the respective rope (41, 42, 43, 44) being connected to the respective spring element (71, 72, 73, 74).
Apparatus according to claim 1 or 2, characterized in that the apparatus (1) comprises a controlling unit being designed to control said drive units (510, 520, 530, 540), in order to adjust said current resulting force (F), wherein the controlling unit is designed to control the drive units (510, 520, 530, 540) such that the current resulting force ( F ) approaches a desired force ( F _des) or that the current position of the node (60) approaches a desired position of the node (60).
Apparatus according to one of the preceding claims, characterized in that the apparatus (1) comprises at least a first and a second rope (41, 42), particularly also a third and a fourth rope (41, 42, 43, 44), wherein
- the first rope (41) extends from its associated drive unit (510) towards a first deflection device (31), is deflected by the first deflection device (31) and then extends towards the node (60),

- the second rope (42) extends from its associated drive unit (520) towards a second deflection device (32), is deflected by the second deflection device (32) and then extends towards the node (60),

- particularly the third rope (43) extends from its associated drive unit (530) towards a third deflection device (33), is deflected by the third deflection device (33) and then extends towards the node (60), and

- particularly the fourth rope (44) extends from its associated drive unit (540) towards a fourth deflection device (34), is deflected by the fourth deflection device (34) and then extends towards the node (60).
Apparatus according to one of the preceding claims, characterized in that the deflection devices are designed to be suspended, particularly from a support frame or from a ceiling of a room.
Apparatus according to one of the claims 1 to 5, characterized in that the apparatus (1) comprises at least a first guide rail (21) running along a longitudinal axis (L) that extends horizontally, wherein particularly the apparatus (1) also comprises a second guide rail (22) running along a longitudinal axis (L') that extends horizontally, wherein particularly each of the two guide rails (21, 22) is designed to be connected to a support structure, particularly to a support frame (10) of the apparatus (1) or to a ceiling of a room, and wherein particularly the two guide rails (21, 22) run parallel with respect to each other, wherein particularly each guide rail (21, 22) is tilted about its longitudinal axis (L, L'), particularly by an angle of 45°.
Apparatus according to claims 4 and 6, characterized in that the first and the second deflection device (31, 32) are slidably connected to the first guide rail (21), so that they can slide along the first guide rail (21) along the longitudinal axis (L) of the first guide rail (21), and wherein particularly the third and the fourth deflection device (33, 34) are slidably connected to the second guide rail (22), so that they can slide along the second guide rail (22) along the longitudinal axis (L') of the second guide rail (22), wherein particularly the deflection devices (31, 32, 33, 34) each comprise a base (340) via which the respective deflection device (31, 32, 33, 34) is slidably connected to the associated guide rail (21, 22), and wherein particularly each deflection device (31, 32, 33, 34) comprises an arm (341) hinged to the base (340) of the respective deflection device (31, 32, 33, 34) so that the respective arm (341) can be pivoted with respect to the respective base (340) about an pivoting axis (A) running parallel to the longitudinal axis (L, L') of the respective guide rail (21, 22), and wherein particularly the deflection devices (31, 32, 33, 34) each comprise a deflection element (344) connected to the respective arm (341), around which deflection element (344) the respective rope (41, 42, 43, 44) is laid for deflecting said rope (41, 42, 43, 44), and wherein particularly the deflection element (344) is a roller that is rotatably connected to the respective arm (341), and wherein particularly an arresting means (C) is provided for each deflection device (31, 32, 33, 34) for arresting the respective deflection device (31, 32, 33, 34) with respect to the associated guide rail (21, 22).
Apparatus according to claim 4 or one of the claims 5 to 7 when referred back to claim 4, characterized in that the first and second deflection device (31, 32) are connected by a connecting element (350) so as to form a first deflection unit (35), and wherein particularly the third and the fourth deflection device (33, 34) are connected by a connecting element (360) so as to form a second deflection unit (36), wherein particularly said connecting elements (350, 360) comprise the same length along the longitudinal axis (L, L') of the respective guide rail (21, 22), and wherein particularly the connecting elements (350, 360) are releasably connected to the respective deflection devices (31, 32; 33, 34), wherein particularly the respective connecting element (350, 360) is a rope member or a rigid rod, and wherein particularly the first deflection unit (35) is arranged along the longitudinal axis (L) of the first guide rail (21) between the drive unit (510) of the first rope (41) and the drive unit (520) of the second rope (42), and wherein particularly the second deflection unit (36) is arranged along the longitudinal axis (L') of the second guide rail (22) between the drive unit (530) of the third rope (43) and the drive unit (540) of the fourth rope (44).
Apparatus according to one of the preceding claims characterized in that the drive units (510, 520, 530, 540) each comprise an actuator (512, 522, 532, 542) being connected to a winch (511, 521, 531, 541), particularly via a flexible coupling (53), around which winch (511, 521, 531, 541) the respective rope (41, 42, 43, 44) is wound, wherein the respective actuator (512, 522, 532, 542) is designed to exert a torque on the respective winch (511, 521, 531, 541) so as to retract or release the respective rope (41, 42, 43, 44), wherein particularly the respective drive unit (510, 520, 530, 540) may comprise a brake for arresting the respective winch (511, 521, 531, 541), and wherein particularly the respective drive unit (510, 520, 530, 540) comprises at least one pressing member (54), particularly a pressure roller being configured to press the respective rope (41, 42, 43, 44) being wound around the respective winch (511, 521, 531, 541) against the respective winch (511, 521, 531, 541), particularly so as to prevent the respective rope (41, 42, 43, 44) from jumping off the associated winch (511, 521, 531, 541) or over a thread.
Apparatus according to one of the preceding claims, characterized in that the apparatus (1) comprises a sensor means for determining a current state ( s ) of the apparatus (1) and the position (w) of the user (4), wherein said current state is particularly defined by the lengths (s _w) of the ropes (41, 42, 43, 44) being unwound from the respective winch (511, 521, 531, 541) and the positions (s _T) of the deflection units (35, 36) along the respective guide rail (21, 22).
Apparatus according to claim 10, characterized in that the controlling unit is designed to calculate the desired rope force ( F _R,des) for each of the ropes (41, 42, 43, 44) depending on the current state ( s ) of the apparatus (1) and the position (w) of the user (4) determined with help of the sensor means, particularly under the condition that
- there is force equilibrium on the node (60),

- there is force equilibrium on the deflection units (35, 36), and

- the deflection units (35, 36) both reside in the same position along the
respective guide rail (21, 22),
wherein the controlling unit is designed to control the drive units (510, 520, 530, 540), particularly the torque (u) exerted by the respective actuator (512, 522, 532, 542) onto the respective winch (511, 521, 531, 541), such that the current rope forces ( F _R) approach the respective desired rope force ( F _R,des) or that the current position of the user (4) approaches a desired position of the user (4), wherein particularly the controlling unit is configured to apply a pre-defined torque to a plurality of the drive units (510, 520, 530, 540) at the same time, particularly in order to let the current rope forces ( F _R) approach the desired rope forces ( F _R,des) faster, wherein particularly the controlling unit is configured to control the torques (u) according to $u = i F_{R, des} + K_{r} (F_{R, des} - F_{R}) + u_{ff},$

with F _R,des being the calculated desired rope forces, i being the transmission ratio of the respective winch, $K_{r} \in R^{nxn}$
being a positive definite rope force feedback matrix containing feedback gains, $n \in N$
being the number of ropes, and u _ff being an optional additional term going to zero in static conditions of the apparatus by means of which a pre-defined torque can be applied to a plurality of the winches (511, 521, 531, 541) at the same time.
Apparatus according to one of the preceding claims, characterized in that the apparatus (1) comprises a bail (80) for coupling the node (60) to the user (4), wherein said bail (80) is rotatably connected to the node (60), so that particularly the bail (80) can be rotated about a vertical axis (z), wherein particularly the bail (80) comprises two opposing free ends (81, 82), wherein particularly each of the two free ends (81, 82) comprises a receptacle for receiving a connection element (96, 97) for connecting a harness (95) to the bail (80), which harness (95) is particularly designed to be attached to the user (4) in order to connect the user (4) to the node (60) via the bail (80), wherein said connection elements (96, 97) are designed to be length adjustable for adapting the apparatus (1) to the user (4).
Method for controlling an apparatus for unloading the body weight of a user, particularly using an apparatus according to at least one of the preceding claims, comprising the steps of:
- calculating torques (u) for a plurality of winches (511, 521, 531, 541),

- exerting the torques (u) onto the winches (511, 521, 531, 541) in order to adjust current rope forces (F _R) acting along ropes (41, 42, 43, 44) coupled to the winches (511, 521, 531, 541), respectively, wherein each rope (41, 42, 43, 44) is connected to a node (60) via a first free end (41 a, 42a, 43a, 44a) of the respective rope (41, 42, 43, 44), to which node (60) a user (4) was coupled in beforehand such that the rope forces ( F _R) add to a current resulting force (F) acting on the user (4) via the node (60), and wherein the ropes (41, 42, 43, 44) are each deflected by a passively displaceable deflection device (31, 32, 33, 34), and

- wherein the torques (u) are calculated such that the position of the node (60) approaches a desired position of the node (60) or that said current resulting force (F) on the user (4) approaches a desired force ( F _des) on the user (4) when the calculated torques (u) are exerted onto the winches (511, 521, 531. 541), wherein particularly a current state ( s ) of the apparatus (1) and a current position (w) of the user (4) is determined, and wherein particularly said torques (u) are calculated depending on said current state ( s ) and said current position (w) of the user (4).
Method according to claim 13, characterized in that the deflection devices (31, 32, 33, 34) pairwise form deflection units (35, 36), such that the two deflection devices (31, 32; 33, 34) of a deflection unit (35, 36) are passively displaceable together, particularly along a first direction (x), wherein particularly a first and a second rope (41, 42) and an associated first deflection unit (35) are provided, and wherein particularly also a third and a fourth rope (43, 44) and an associated second deflection (36) unit are provided, and wherein particularly said current state ( s ) is particularly defined by the lengths ( s _w) of the ropes (41, 42, 43, 44) being unwound from the respective winch (511, 521, 531, 541) and the positions ( s _T) of said deflection units (35, 36) along the first direction (x).
Method according to claim 14, characterized in that said torques (u) are determined by means of an inner control loop that calculates desired rope forces ( F _R,des) for each of the ropes (41, 42, 43, 44), which are determined depending on the current state ( s ) of the apparatus (1) and the current position (w) of the user (4) requiring the condition that
- there is force equilibrium on the node (60),

- there is force equilibrium on the deflection units (35, 36), and

- particularly the deflection units (35, 36) reside in the same position along
the first direction (x),
and wherein particularly a pre-defined torque is applied to a plurality of the winches (510, 520, 530, 540) at the same time, particularly in order to let the current rope forces ( F _R) approach the desired rope forces ( F _R,des) faster, wherein particularly the torques (u) are determined according to $u = i F_{R, des} + K_{r} (F_{R, des} - F_{R}) + u_{ff},$

with F _R,des being the calculated desired rope forces, i being the transmission ratio of the respective winch, $K_{r} \in R^{nxn}$
being a positive definite rope force feedback matrix containing feedback gains, $n \in N$
being the number of ropes, and u _ff being an optional additional term going to zero in static conditions of the apparatus (1).